CMMG RDB + Fluted chamber?

Ever wonder what would happen if you combined the Radially Delayed Blowback action with a fluted chamber found on the HK MP5 Roller Delayd Blowback?

This is obviously not needed.  I would argue that it isn’t ‘needed’ on a real MP5 either as I have a friend that supports a MG rental range and has been swapping barrels for their rental MP5’s with cheap non-fluted barrels and they work fine.  I did this out of curiosity to see what what would happen.

As you can see above the diameter of the trunion area of the MP5K barrel is pretty small and leaves very little should for an M16 extension.  It took me 3 times to get it right and I also had to remove .005″ off the breach face reliable operation.

I know the above comparison isn’t a perfect like for like test as their is a discrepancy on the different barrel lengths of 5.85 vs 7.5 but I am not going to bother cutting down another barrel to exactly 5.85 just for this testing.

Conclusion is it works and seems to add reliability since it functions without an extractor even installed in the bolt.  I don’t mind the reduction in the cyclic rate but if the reason there is a reduction is due to additional drag from scarring the brass that isn’t seem like a good idea.  Could also be that the flutes in the chamber have burrs in them and could use a little de-burring which I haven’t looked into yet.  These barrels are NOT chrome lined so polishing the flutes for any burrs shouldn’t be an issue.  Or maybe the scarring will go away after running it more.